1. Filed of the Invention
The present invention relates to an optical scanning device, and more particularly to an optical scanning device for irradiating a photosensitive drum with a light beam to form an electrostatic latent image on the photosensitive drum.
2. Description of Related Art
An example of well-known conventional optical scanning devices is a post-objective type optical scanning device (which will be hereinafter referred to merely as an optical scanning device) as disclosed by Japanese Patent Laid-Open Publication No. 5-241094. In the optical scanning device, a polygon mirror having cylindrical or spherical reflecting surfaces is employed, and thereby, the necessity of providing a scanning lens between the polygon mirror and the photosensitive drum is eliminated.
However, since the reflecting surfaces of the polygon mirror are not planar, the manufacturing cost of the optical scanning device is high.